As a method of forming a film on a semiconductor wafer (hereinafter, referred to as “wafer”), there is known an atomic layer deposition (ALD) method in which a raw material gas and a reaction gas are sequentially supplied to the wafer to deposit a molecular layer (or an atomic layer) of a reaction product on the surface of the wafer, thereby forming a thin film on the wafer. When the film forming process according to the ALD method is performed on the wafer in which asperities are formed in a circuit pattern, a film conforming to the asperities (a film having a conformal shape) is formed.
Meanwhile, as a method of forming a contact hole, a self-aligned contact hole forming method is used in view of the fact that a pattern is miniaturized and a high accuracy is also required for pattern alignment. Further, since three-dimensionalization of the semiconductor device is further developing, for example, a contact hole or groove portion tends to be minute and an aspect ratio tends to be larger. For this reason, for example, when a process of filling the self-aligned contact hole with a silicon nitride film by the ALD method is performed, there is concern that a clearance such as a void, a seam or the like may be created in a filled portion (silicon nitride film) within the contact hole.
For example, a technique for forming a fluorocarbon film (CF film) is known. The film is formed within a depression formed in an aluminum layer by using a CF-based gas and a CH-based gas to fill the depression. The CF film is etched using an oxygen gas while halting the filling of the depression and then the CF film filling process is performed. Unlike the present disclosure, however, this technique does not consider a difference in incubation time among regions in which a film is formed.